android rolate旋转角度90度，无变化

代码如下？用了旋转但是效果和没用一样

 protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        int mCircleXY = getMeasuredWidth();
        int mRadius = (int) (mCircleXY / 2);
        RectF mRectF = new RectF(0, 0, mCircleXY, mCircleXY);
        Paint p = new Paint();
        p.setStyle(Style.FILL);
        p.setColor(mColor);

        // 绘制一个圆弧
        canvas.drawArc(mRectF, 270, sweap, true, p);
        canvas.save();
        // 旋转90度，然而没有效果
        canvas.rotate(90, mCircleXY / 2, mCircleXY / 2);
        super.onDraw(canvas);
        canvas.restore();
    }